Optofluidic smart glass with wide angular performance
Date
2019
Authors
Journal Title
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Volume Title
Publisher
University of Delaware
Abstract
Smart glass or switchable transparency panels are being commercialized for applications ranging from privacy panels to controlling solar load for buildings and vehicles. However, the technologies that have been developed such as electrochromic, polymer dispersed liquid crystal, and suspended particle devices are complex and expensive, and additionally switch from partial transparency to a tinted or scattering state, not having a highly reflective state, which limits applications. Here is shown an optofluidic smart glass which may have 10x lower cost than current technologies. It is based upon a reflective structure that switches to transmissive by introducing an index-matching fluid. Previously, we have shown such a panel that consists of a solid plastic corner-cube array with a thin cavity behind it. With air in the cavity the panel is highly reflective based upon total internal reflection. There inexpensive index matching fluids were shown that when pumped into the cavity result in near-perfect transparency. However, corner-cube array panels transmit at angles larger than 20 degrees in the reflective state. Here, a two-layer structure is shown consisting of two one-dimensional solid corner reflector arrays with the layers having rotated axes. Rays beyond the TIR angle for one layer are refracted below the TIR angle for the second layer. Each layer has a cavity layer for introducing index matching fluid, and high transmission switching up to 60 degrees is shown. Also, here, the concept of clarity is introduced for the fluid-filled, transparent state of the panel. For materials shown here, with a refractive index difference between the panel and fluid of 0.013, features as small as 2 cm at 1 meter behind the panel can be resolved. To achieve clarity, for example being able to resolve features as small as 0.5 cm at 1 meter, the refractive index difference must be smaller than 0.003. To further minimize the index difference, method of mixed fluid is used. The optimized transparency for VeroClear is achieved using mineral oil and anise oil mixture. This method has nearly perfect matching for VeroClear at room temperature.
Description
Keywords
Optofluidic smart glass, Wide angular performance